> Suppose you have a good commit 123 were all your tests pass for some project, you cut a release, and deploy it.

And you've personally done this for a larger project with significant amount of changes and a longer duration (like maybe 6 months to a year)?

I'm struggling to understand why you would eliminate branches? It would increase complexity, work and duration of projects to try to shoehorn 2 different system models into one system. Your 6 month project just shifted to a 12 to 24 month project.